1. Field of the Invention
The invention relates in general to an etching method for semiconductor element, and more particularly to an etching method for semiconductor element using an anti-reflective layer and a hard mask.
2. Description of the Related Art
As the technology of manufacturing semiconductor device continues to shrink, the size of electronic elements continues to be reduced and element density continues to increase. Facing the trend of concentrating and reducing semiconductor elements, the photolithography and etching process for manufacturing semiconductor element is encountering huge challenges.
Take the contact hole manufacturing process of semiconductor element for example. Referring to FIG. 1, a cross-sectional view of conventionally forming a contact hole of a semiconductor element is shown. The substrate 10 includes an insulating portion 14 and a conductive portion 12. The insulating portion 14 is disposed on the conductive portion 12. After the patterned photo resist layer 16 is formed on the substrate 10, a opening 14a is formed on the insulating portion 14 corresponding to the pattern of the patterned photo resist layer 16 by the reactive ion etching (RIE) method until the conductive portion 12 at the bottom is exposed. Since the aspect ratio of the opening 14a is large, the patterned photo resist layer 16 is normally depleted under continuous ion impact during the application of the reactive ion etching method. The insulating portion 14 shielded underneath will be exposed and etched by ions, and the to-be-formed structure will be damaged. In general, damage-free structure can be obtained by means of increasing the photo resist thickness. However, photo resist will collapse as photo resist thickness is too high. The peeled part of the photo resist layer may drop into the opening or affect the precision of the etched pattern.
Besides, during the process of exposing the photo resist layer by deep ultra violet light (DUV light) for instance, the substrate under the photo resist layer reflects the deep ultra violet light, such that part of the preserved photo resist layer is undercut and the resolution of exposure is affected.